My Built-in WIFI in Raspberry PI 3 has really low range (signal starts to decay after 10 meters of distance from the router)I would like to disable my built-in wifi and install a USB Wifi adapter instead. I've read that Wtware supports most of the newest Realtek Chipset models and i just bought one.How should i proceed ?

Connect USB WiFi adapter and run. If wtware has driver for it, it will use usb device instead of built-in.If it still uses built-in, connect to wifi (usb one should be connected!) and send us a log: http://wtware.com/docs5/logs.html